mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/mm.h>
  11 #include <linux/sched.h>
  12 #include <linux/highmem.h>
  13 #include <linux/hugetlb.h>
  14 #include <linux/mmu_notifier.h>
  15 #include <linux/rmap.h>
  16 #include <linux/swap.h>
  17 #include <linux/shrinker.h>
  18 #include <linux/mm_inline.h>
  19 #include <linux/dax.h>
  20 #include <linux/kthread.h>
  21 #include <linux/khugepaged.h>
  22 #include <linux/freezer.h>
  23 #include <linux/mman.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/migrate.h>
  26 #include <linux/hashtable.h>
  27 #include <linux/userfaultfd_k.h>
  28
  29 #include <asm/tlb.h>
  30 #include <asm/pgalloc.h>
  31 #include "internal.h"
  32
  33 /*
  34  * By default transparent hugepage support is disabled in order that avoid
  35  * to risk increase the memory footprint of applications without a guaranteed
  36  * benefit. When transparent hugepage support is enabled, is for all mappings,
  37  * and khugepaged scans all mappings.
  38  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  39  * for all hugepage allocations.
  40  */
  41 unsigned long transparent_hugepage_flags __read_mostly =
  42 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  43         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  44 #endif
  45 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  46         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  47 #endif
  48         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  49         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  50         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  51
  52 /* default scan 8*512 pte (or vmas) every 30 second */
  53 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  54 static unsigned int khugepaged_pages_collapsed;
  55 static unsigned int khugepaged_full_scans;
  56 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  57 /* during fragmentation poll the hugepage allocator once every minute */
  58 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  59 static struct task_struct *khugepaged_thread __read_mostly;
  60 static DEFINE_MUTEX(khugepaged_mutex);
  61 static DEFINE_SPINLOCK(khugepaged_mm_lock);
  62 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  63 /*
  64  * default collapse hugepages if there is at least one pte mapped like
  65  * it would have happened if the vma was large enough during page
  66  * fault.
  67  */
  68 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  69
  70 static int khugepaged(void *none);
  71 static int khugepaged_slab_init(void);
  72 static void khugepaged_slab_exit(void);
  73
  74 #define MM_SLOTS_HASH_BITS 10
  75 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
  76
  77 static struct kmem_cache *mm_slot_cache __read_mostly;
  78
  79 /**
  80  * struct mm_slot - hash lookup from mm to mm_slot
  81  * @hash: hash collision list
  82  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  83  * @mm: the mm that this information is valid for
  84  */
  85 struct mm_slot {
  86         struct hlist_node hash;
  87         struct list_head mm_node;
  88         struct mm_struct *mm;
  89 };
  90
  91 /**
  92  * struct khugepaged_scan - cursor for scanning
  93  * @mm_head: the head of the mm list to scan
  94  * @mm_slot: the current mm_slot we are scanning
  95  * @address: the next address inside that to be scanned
  96  *
  97  * There is only the one khugepaged_scan instance of this cursor structure.
  98  */
  99 struct khugepaged_scan {
 100         struct list_head mm_head;
 101         struct mm_slot *mm_slot;
 102         unsigned long address;
 103 };
 104 static struct khugepaged_scan khugepaged_scan = {
 105         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 106 };
 107
 108
 109 static void set_recommended_min_free_kbytes(void)
 110 {
 111         struct zone *zone;
 112         int nr_zones = 0;
 113         unsigned long recommended_min;
 114
 115         for_each_populated_zone(zone)
 116                 nr_zones++;
 117
 118         /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
 119         recommended_min = pageblock_nr_pages * nr_zones * 2;
 120
 121         /*
 122          * Make sure that on average at least two pageblocks are almost free
 123          * of another type, one for a migratetype to fall back to and a
 124          * second to avoid subsequent fallbacks of other types There are 3
 125          * MIGRATE_TYPES we care about.
 126          */
 127         recommended_min += pageblock_nr_pages * nr_zones *
 128                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 129
 130         /* don't ever allow to reserve more than 5% of the lowmem */
 131         recommended_min = min(recommended_min,
 132                               (unsigned long) nr_free_buffer_pages() / 20);
 133         recommended_min <<= (PAGE_SHIFT-10);
 134
 135         if (recommended_min > min_free_kbytes) {
 136                 if (user_min_free_kbytes >= 0)
 137                         pr_info("raising min_free_kbytes from %d to %lu "
 138                                 "to help transparent hugepage allocations\n",
 139                                 min_free_kbytes, recommended_min);
 140
 141                 min_free_kbytes = recommended_min;
 142         }
 143         setup_per_zone_wmarks();
 144 }
 145
 146 static int start_stop_khugepaged(void)
 147 {
 148         int err = 0;
 149         if (khugepaged_enabled()) {
 150                 if (!khugepaged_thread)
 151                         khugepaged_thread = kthread_run(khugepaged, NULL,
 152                                                         "khugepaged");
 153                 if (unlikely(IS_ERR(khugepaged_thread))) {
 154                         pr_err("khugepaged: kthread_run(khugepaged) failed\n");
 155                         err = PTR_ERR(khugepaged_thread);
 156                         khugepaged_thread = NULL;
 157                         goto fail;
 158                 }
 159
 160                 if (!list_empty(&khugepaged_scan.mm_head))
 161                         wake_up_interruptible(&khugepaged_wait);
 162
 163                 set_recommended_min_free_kbytes();
 164         } else if (khugepaged_thread) {
 165                 kthread_stop(khugepaged_thread);
 166                 khugepaged_thread = NULL;
 167         }
 168 fail:
 169         return err;
 170 }
 171
 172 static atomic_t huge_zero_refcount;
 173 struct page *huge_zero_page __read_mostly;
 174
 175 struct page *get_huge_zero_page(void)
 176 {
 177         struct page *zero_page;
 178 retry:
 179         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 180                 return READ_ONCE(huge_zero_page);
 181
 182         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 183                         HPAGE_PMD_ORDER);
 184         if (!zero_page) {
 185                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 186                 return NULL;
 187         }
 188         count_vm_event(THP_ZERO_PAGE_ALLOC);
 189         preempt_disable();
 190         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 191                 preempt_enable();
 192                 __free_pages(zero_page, compound_order(zero_page));
 193                 goto retry;
 194         }
 195
 196         /* We take additional reference here. It will be put back by shrinker */
 197         atomic_set(&huge_zero_refcount, 2);
 198         preempt_enable();
 199         return READ_ONCE(huge_zero_page);
 200 }
 201
 202 static void put_huge_zero_page(void)
 203 {
 204         /*
 205          * Counter should never go to zero here. Only shrinker can put
 206          * last reference.
 207          */
 208         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 209 }
 210
 211 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 212                                         struct shrink_control *sc)
 213 {
 214         /* we can free zero page only if last reference remains */
 215         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 216 }
 217
 218 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 219                                        struct shrink_control *sc)
 220 {
 221         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 222                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 223                 BUG_ON(zero_page == NULL);
 224                 __free_pages(zero_page, compound_order(zero_page));
 225                 return HPAGE_PMD_NR;
 226         }
 227
 228         return 0;
 229 }
 230
 231 static struct shrinker huge_zero_page_shrinker = {
 232         .count_objects = shrink_huge_zero_page_count,
 233         .scan_objects = shrink_huge_zero_page_scan,
 234         .seeks = DEFAULT_SEEKS,
 235 };
 236
 237 #ifdef CONFIG_SYSFS
 238
 239 static ssize_t double_flag_show(struct kobject *kobj,
 240                                 struct kobj_attribute *attr, char *buf,
 241                                 enum transparent_hugepage_flag enabled,
 242                                 enum transparent_hugepage_flag req_madv)
 243 {
 244         if (test_bit(enabled, &transparent_hugepage_flags)) {
 245                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 246                 return sprintf(buf, "[always] madvise never\n");
 247         } else if (test_bit(req_madv, &transparent_hugepage_flags))
 248                 return sprintf(buf, "always [madvise] never\n");
 249         else
 250                 return sprintf(buf, "always madvise [never]\n");
 251 }
 252 static ssize_t double_flag_store(struct kobject *kobj,
 253                                  struct kobj_attribute *attr,
 254                                  const char *buf, size_t count,
 255                                  enum transparent_hugepage_flag enabled,
 256                                  enum transparent_hugepage_flag req_madv)
 257 {
 258         if (!memcmp("always", buf,
 259                     min(sizeof("always")-1, count))) {
 260                 set_bit(enabled, &transparent_hugepage_flags);
 261                 clear_bit(req_madv, &transparent_hugepage_flags);
 262         } else if (!memcmp("madvise", buf,
 263                            min(sizeof("madvise")-1, count))) {
 264                 clear_bit(enabled, &transparent_hugepage_flags);
 265                 set_bit(req_madv, &transparent_hugepage_flags);
 266         } else if (!memcmp("never", buf,
 267                            min(sizeof("never")-1, count))) {
 268                 clear_bit(enabled, &transparent_hugepage_flags);
 269                 clear_bit(req_madv, &transparent_hugepage_flags);
 270         } else
 271                 return -EINVAL;
 272
 273         return count;
 274 }
 275
 276 static ssize_t enabled_show(struct kobject *kobj,
 277                             struct kobj_attribute *attr, char *buf)
 278 {
 279         return double_flag_show(kobj, attr, buf,
 280                                 TRANSPARENT_HUGEPAGE_FLAG,
 281                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 282 }
 283 static ssize_t enabled_store(struct kobject *kobj,
 284                              struct kobj_attribute *attr,
 285                              const char *buf, size_t count)
 286 {
 287         ssize_t ret;
 288
 289         ret = double_flag_store(kobj, attr, buf, count,
 290                                 TRANSPARENT_HUGEPAGE_FLAG,
 291                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 292
 293         if (ret > 0) {
 294                 int err;
 295
 296                 mutex_lock(&khugepaged_mutex);
 297                 err = start_stop_khugepaged();
 298                 mutex_unlock(&khugepaged_mutex);
 299
 300                 if (err)
 301                         ret = err;
 302         }
 303
 304         return ret;
 305 }
 306 static struct kobj_attribute enabled_attr =
 307         __ATTR(enabled, 0644, enabled_show, enabled_store);
 308
 309 static ssize_t single_flag_show(struct kobject *kobj,
 310                                 struct kobj_attribute *attr, char *buf,
 311                                 enum transparent_hugepage_flag flag)
 312 {
 313         return sprintf(buf, "%d\n",
 314                        !!test_bit(flag, &transparent_hugepage_flags));
 315 }
 316
 317 static ssize_t single_flag_store(struct kobject *kobj,
 318                                  struct kobj_attribute *attr,
 319                                  const char *buf, size_t count,
 320                                  enum transparent_hugepage_flag flag)
 321 {
 322         unsigned long value;
 323         int ret;
 324
 325         ret = kstrtoul(buf, 10, &value);
 326         if (ret < 0)
 327                 return ret;
 328         if (value > 1)
 329                 return -EINVAL;
 330
 331         if (value)
 332                 set_bit(flag, &transparent_hugepage_flags);
 333         else
 334                 clear_bit(flag, &transparent_hugepage_flags);
 335
 336         return count;
 337 }
 338
 339 /*
 340  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 341  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 342  * memory just to allocate one more hugepage.
 343  */
 344 static ssize_t defrag_show(struct kobject *kobj,
 345                            struct kobj_attribute *attr, char *buf)
 346 {
 347         return double_flag_show(kobj, attr, buf,
 348                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 349                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 350 }
 351 static ssize_t defrag_store(struct kobject *kobj,
 352                             struct kobj_attribute *attr,
 353                             const char *buf, size_t count)
 354 {
 355         return double_flag_store(kobj, attr, buf, count,
 356                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 357                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 358 }
 359 static struct kobj_attribute defrag_attr =
 360         __ATTR(defrag, 0644, defrag_show, defrag_store);
 361
 362 static ssize_t use_zero_page_show(struct kobject *kobj,
 363                 struct kobj_attribute *attr, char *buf)
 364 {
 365         return single_flag_show(kobj, attr, buf,
 366                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 367 }
 368 static ssize_t use_zero_page_store(struct kobject *kobj,
 369                 struct kobj_attribute *attr, const char *buf, size_t count)
 370 {
 371         return single_flag_store(kobj, attr, buf, count,
 372                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 373 }
 374 static struct kobj_attribute use_zero_page_attr =
 375         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 376 #ifdef CONFIG_DEBUG_VM
 377 static ssize_t debug_cow_show(struct kobject *kobj,
 378                                 struct kobj_attribute *attr, char *buf)
 379 {
 380         return single_flag_show(kobj, attr, buf,
 381                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 382 }
 383 static ssize_t debug_cow_store(struct kobject *kobj,
 384                                struct kobj_attribute *attr,
 385                                const char *buf, size_t count)
 386 {
 387         return single_flag_store(kobj, attr, buf, count,
 388                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 389 }
 390 static struct kobj_attribute debug_cow_attr =
 391         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 392 #endif /* CONFIG_DEBUG_VM */
 393
 394 static struct attribute *hugepage_attr[] = {
 395         &enabled_attr.attr,
 396         &defrag_attr.attr,
 397         &use_zero_page_attr.attr,
 398 #ifdef CONFIG_DEBUG_VM
 399         &debug_cow_attr.attr,
 400 #endif
 401         NULL,
 402 };
 403
 404 static struct attribute_group hugepage_attr_group = {
 405         .attrs = hugepage_attr,
 406 };
 407
 408 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 409                                          struct kobj_attribute *attr,
 410                                          char *buf)
 411 {
 412         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 413 }
 414
 415 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 416                                           struct kobj_attribute *attr,
 417                                           const char *buf, size_t count)
 418 {
 419         unsigned long msecs;
 420         int err;
 421
 422         err = kstrtoul(buf, 10, &msecs);
 423         if (err || msecs > UINT_MAX)
 424                 return -EINVAL;
 425
 426         khugepaged_scan_sleep_millisecs = msecs;
 427         wake_up_interruptible(&khugepaged_wait);
 428
 429         return count;
 430 }
 431 static struct kobj_attribute scan_sleep_millisecs_attr =
 432         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 433                scan_sleep_millisecs_store);
 434
 435 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 436                                           struct kobj_attribute *attr,
 437                                           char *buf)
 438 {
 439         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 440 }
 441
 442 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 443                                            struct kobj_attribute *attr,
 444                                            const char *buf, size_t count)
 445 {
 446         unsigned long msecs;
 447         int err;
 448
 449         err = kstrtoul(buf, 10, &msecs);
 450         if (err || msecs > UINT_MAX)
 451                 return -EINVAL;
 452
 453         khugepaged_alloc_sleep_millisecs = msecs;
 454         wake_up_interruptible(&khugepaged_wait);
 455
 456         return count;
 457 }
 458 static struct kobj_attribute alloc_sleep_millisecs_attr =
 459         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 460                alloc_sleep_millisecs_store);
 461
 462 static ssize_t pages_to_scan_show(struct kobject *kobj,
 463                                   struct kobj_attribute *attr,
 464                                   char *buf)
 465 {
 466         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 467 }
 468 static ssize_t pages_to_scan_store(struct kobject *kobj,
 469                                    struct kobj_attribute *attr,
 470                                    const char *buf, size_t count)
 471 {
 472         int err;
 473         unsigned long pages;
 474
 475         err = kstrtoul(buf, 10, &pages);
 476         if (err || !pages || pages > UINT_MAX)
 477                 return -EINVAL;
 478
 479         khugepaged_pages_to_scan = pages;
 480
 481         return count;
 482 }
 483 static struct kobj_attribute pages_to_scan_attr =
 484         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 485                pages_to_scan_store);
 486
 487 static ssize_t pages_collapsed_show(struct kobject *kobj,
 488                                     struct kobj_attribute *attr,
 489                                     char *buf)
 490 {
 491         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 492 }
 493 static struct kobj_attribute pages_collapsed_attr =
 494         __ATTR_RO(pages_collapsed);
 495
 496 static ssize_t full_scans_show(struct kobject *kobj,
 497                                struct kobj_attribute *attr,
 498                                char *buf)
 499 {
 500         return sprintf(buf, "%u\n", khugepaged_full_scans);
 501 }
 502 static struct kobj_attribute full_scans_attr =
 503         __ATTR_RO(full_scans);
 504
 505 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 506                                       struct kobj_attribute *attr, char *buf)
 507 {
 508         return single_flag_show(kobj, attr, buf,
 509                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 510 }
 511 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 512                                        struct kobj_attribute *attr,
 513                                        const char *buf, size_t count)
 514 {
 515         return single_flag_store(kobj, attr, buf, count,
 516                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 517 }
 518 static struct kobj_attribute khugepaged_defrag_attr =
 519         __ATTR(defrag, 0644, khugepaged_defrag_show,
 520                khugepaged_defrag_store);
 521
 522 /*
 523  * max_ptes_none controls if khugepaged should collapse hugepages over
 524  * any unmapped ptes in turn potentially increasing the memory
 525  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 526  * reduce the available free memory in the system as it
 527  * runs. Increasing max_ptes_none will instead potentially reduce the
 528  * free memory in the system during the khugepaged scan.
 529  */
 530 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 531                                              struct kobj_attribute *attr,
 532                                              char *buf)
 533 {
 534         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 535 }
 536 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 537                                               struct kobj_attribute *attr,
 538                                               const char *buf, size_t count)
 539 {
 540         int err;
 541         unsigned long max_ptes_none;
 542
 543         err = kstrtoul(buf, 10, &max_ptes_none);
 544         if (err || max_ptes_none > HPAGE_PMD_NR-1)
 545                 return -EINVAL;
 546
 547         khugepaged_max_ptes_none = max_ptes_none;
 548
 549         return count;
 550 }
 551 static struct kobj_attribute khugepaged_max_ptes_none_attr =
 552         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 553                khugepaged_max_ptes_none_store);
 554
 555 static struct attribute *khugepaged_attr[] = {
 556         &khugepaged_defrag_attr.attr,
 557         &khugepaged_max_ptes_none_attr.attr,
 558         &pages_to_scan_attr.attr,
 559         &pages_collapsed_attr.attr,
 560         &full_scans_attr.attr,
 561         &scan_sleep_millisecs_attr.attr,
 562         &alloc_sleep_millisecs_attr.attr,
 563         NULL,
 564 };
 565
 566 static struct attribute_group khugepaged_attr_group = {
 567         .attrs = khugepaged_attr,
 568         .name = "khugepaged",
 569 };
 570
 571 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 572 {
 573         int err;
 574
 575         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 576         if (unlikely(!*hugepage_kobj)) {
 577                 pr_err("failed to create transparent hugepage kobject\n");
 578                 return -ENOMEM;
 579         }
 580
 581         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 582         if (err) {
 583                 pr_err("failed to register transparent hugepage group\n");
 584                 goto delete_obj;
 585         }
 586
 587         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 588         if (err) {
 589                 pr_err("failed to register transparent hugepage group\n");
 590                 goto remove_hp_group;
 591         }
 592
 593         return 0;
 594
 595 remove_hp_group:
 596         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 597 delete_obj:
 598         kobject_put(*hugepage_kobj);
 599         return err;
 600 }
 601
 602 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 603 {
 604         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 605         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 606         kobject_put(hugepage_kobj);
 607 }
 608 #else
 609 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 610 {
 611         return 0;
 612 }
 613
 614 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 615 {
 616 }
 617 #endif /* CONFIG_SYSFS */
 618
 619 static int __init hugepage_init(void)
 620 {
 621         int err;
 622         struct kobject *hugepage_kobj;
 623
 624         if (!has_transparent_hugepage()) {
 625                 transparent_hugepage_flags = 0;
 626                 return -EINVAL;
 627         }
 628
 629         err = hugepage_init_sysfs(&hugepage_kobj);
 630         if (err)
 631                 goto err_sysfs;
 632
 633         err = khugepaged_slab_init();
 634         if (err)
 635                 goto err_slab;
 636
 637         err = register_shrinker(&huge_zero_page_shrinker);
 638         if (err)
 639                 goto err_hzp_shrinker;
 640
 641         /*
 642          * By default disable transparent hugepages on smaller systems,
 643          * where the extra memory used could hurt more than TLB overhead
 644          * is likely to save.  The admin can still enable it through /sys.
 645          */
 646         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 647                 transparent_hugepage_flags = 0;
 648                 return 0;
 649         }
 650
 651         err = start_stop_khugepaged();
 652         if (err)
 653                 goto err_khugepaged;
 654
 655         return 0;
 656 err_khugepaged:
 657         unregister_shrinker(&huge_zero_page_shrinker);
 658 err_hzp_shrinker:
 659         khugepaged_slab_exit();
 660 err_slab:
 661         hugepage_exit_sysfs(hugepage_kobj);
 662 err_sysfs:
 663         return err;
 664 }
 665 subsys_initcall(hugepage_init);
 666
 667 static int __init setup_transparent_hugepage(char *str)
 668 {
 669         int ret = 0;
 670         if (!str)
 671                 goto out;
 672         if (!strcmp(str, "always")) {
 673                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 674                         &transparent_hugepage_flags);
 675                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 676                           &transparent_hugepage_flags);
 677                 ret = 1;
 678         } else if (!strcmp(str, "madvise")) {
 679                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 680                           &transparent_hugepage_flags);
 681                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 682                         &transparent_hugepage_flags);
 683                 ret = 1;
 684         } else if (!strcmp(str, "never")) {
 685                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 686                           &transparent_hugepage_flags);
 687                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 688                           &transparent_hugepage_flags);
 689                 ret = 1;
 690         }
 691 out:
 692         if (!ret)
 693                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 694         return ret;
 695 }
 696 __setup("transparent_hugepage=", setup_transparent_hugepage);
 697
 698 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 699 {
 700         if (likely(vma->vm_flags & VM_WRITE))
 701                 pmd = pmd_mkwrite(pmd);
 702         return pmd;
 703 }
 704
 705 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
 706 {
 707         pmd_t entry;
 708         entry = mk_pmd(page, prot);
 709         entry = pmd_mkhuge(entry);
 710         return entry;
 711 }
 712
 713 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 714                                         struct vm_area_struct *vma,
 715                                         unsigned long address, pmd_t *pmd,
 716                                         struct page *page, gfp_t gfp,
 717                                         unsigned int flags)
 718 {
 719         struct mem_cgroup *memcg;
 720         pgtable_t pgtable;
 721         spinlock_t *ptl;
 722         unsigned long haddr = address & HPAGE_PMD_MASK;
 723
 724         VM_BUG_ON_PAGE(!PageCompound(page), page);
 725
 726         if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) {
 727                 put_page(page);
 728                 count_vm_event(THP_FAULT_FALLBACK);
 729                 return VM_FAULT_FALLBACK;
 730         }
 731
 732         pgtable = pte_alloc_one(mm, haddr);
 733         if (unlikely(!pgtable)) {
 734                 mem_cgroup_cancel_charge(page, memcg);
 735                 put_page(page);
 736                 return VM_FAULT_OOM;
 737         }
 738
 739         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 740         /*
 741          * The memory barrier inside __SetPageUptodate makes sure that
 742          * clear_huge_page writes become visible before the set_pmd_at()
 743          * write.
 744          */
 745         __SetPageUptodate(page);
 746
 747         ptl = pmd_lock(mm, pmd);
 748         if (unlikely(!pmd_none(*pmd))) {
 749                 spin_unlock(ptl);
 750                 mem_cgroup_cancel_charge(page, memcg);
 751                 put_page(page);
 752                 pte_free(mm, pgtable);
 753         } else {
 754                 pmd_t entry;
 755
 756                 /* Deliver the page fault to userland */
 757                 if (userfaultfd_missing(vma)) {
 758                         int ret;
 759
 760                         spin_unlock(ptl);
 761                         mem_cgroup_cancel_charge(page, memcg);
 762                         put_page(page);
 763                         pte_free(mm, pgtable);
 764                         ret = handle_userfault(vma, address, flags,
 765                                                VM_UFFD_MISSING);
 766                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 767                         return ret;
 768                 }
 769
 770                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 771                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 772                 page_add_new_anon_rmap(page, vma, haddr);
 773                 mem_cgroup_commit_charge(page, memcg, false);
 774                 lru_cache_add_active_or_unevictable(page, vma);
 775                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 776                 set_pmd_at(mm, haddr, pmd, entry);
 777                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 778                 atomic_long_inc(&mm->nr_ptes);
 779                 spin_unlock(ptl);
 780                 count_vm_event(THP_FAULT_ALLOC);
 781         }
 782
 783         return 0;
 784 }
 785
 786 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 787 {
 788         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 789 }
 790
 791 /* Caller must hold page table lock. */
 792 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 793                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 794                 struct page *zero_page)
 795 {
 796         pmd_t entry;
 797         if (!pmd_none(*pmd))
 798                 return false;
 799         entry = mk_pmd(zero_page, vma->vm_page_prot);
 800         entry = pmd_mkhuge(entry);
 801         pgtable_trans_huge_deposit(mm, pmd, pgtable);
 802         set_pmd_at(mm, haddr, pmd, entry);
 803         atomic_long_inc(&mm->nr_ptes);
 804         return true;
 805 }
 806
 807 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 808                                unsigned long address, pmd_t *pmd,
 809                                unsigned int flags)
 810 {
 811         gfp_t gfp;
 812         struct page *page;
 813         unsigned long haddr = address & HPAGE_PMD_MASK;
 814
 815         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 816                 return VM_FAULT_FALLBACK;
 817         if (unlikely(anon_vma_prepare(vma)))
 818                 return VM_FAULT_OOM;
 819         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 820                 return VM_FAULT_OOM;
 821         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
 822                         transparent_hugepage_use_zero_page()) {
 823                 spinlock_t *ptl;
 824                 pgtable_t pgtable;
 825                 struct page *zero_page;
 826                 bool set;
 827                 int ret;
 828                 pgtable = pte_alloc_one(mm, haddr);
 829                 if (unlikely(!pgtable))
 830                         return VM_FAULT_OOM;
 831                 zero_page = get_huge_zero_page();
 832                 if (unlikely(!zero_page)) {
 833                         pte_free(mm, pgtable);
 834                         count_vm_event(THP_FAULT_FALLBACK);
 835                         return VM_FAULT_FALLBACK;
 836                 }
 837                 ptl = pmd_lock(mm, pmd);
 838                 ret = 0;
 839                 set = false;
 840                 if (pmd_none(*pmd)) {
 841                         if (userfaultfd_missing(vma)) {
 842                                 spin_unlock(ptl);
 843                                 ret = handle_userfault(vma, address, flags,
 844                                                        VM_UFFD_MISSING);
 845                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 846                         } else {
 847                                 set_huge_zero_page(pgtable, mm, vma,
 848                                                    haddr, pmd,
 849                                                    zero_page);
 850                                 spin_unlock(ptl);
 851                                 set = true;
 852                         }
 853                 } else
 854                         spin_unlock(ptl);
 855                 if (!set) {
 856                         pte_free(mm, pgtable);
 857                         put_huge_zero_page();
 858                 }
 859                 return ret;
 860         }
 861         gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
 862         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 863         if (unlikely(!page)) {
 864                 count_vm_event(THP_FAULT_FALLBACK);
 865                 return VM_FAULT_FALLBACK;
 866         }
 867         return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
 868                                             flags);
 869 }
 870
 871 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 872                 pmd_t *pmd, unsigned long pfn, pgprot_t prot, bool write)
 873 {
 874         struct mm_struct *mm = vma->vm_mm;
 875         pmd_t entry;
 876         spinlock_t *ptl;
 877
 878         ptl = pmd_lock(mm, pmd);
 879         if (pmd_none(*pmd)) {
 880                 entry = pmd_mkhuge(pfn_pmd(pfn, prot));
 881                 if (write) {
 882                         entry = pmd_mkyoung(pmd_mkdirty(entry));
 883                         entry = maybe_pmd_mkwrite(entry, vma);
 884                 }
 885                 set_pmd_at(mm, addr, pmd, entry);
 886                 update_mmu_cache_pmd(vma, addr, pmd);
 887         }
 888         spin_unlock(ptl);
 889 }
 890
 891 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 892                         pmd_t *pmd, unsigned long pfn, bool write)
 893 {
 894         pgprot_t pgprot = vma->vm_page_prot;
 895         /*
 896          * If we had pmd_special, we could avoid all these restrictions,
 897          * but we need to be consistent with PTEs and architectures that
 898          * can't support a 'special' bit.
 899          */
 900         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 901         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 902                                                 (VM_PFNMAP|VM_MIXEDMAP));
 903         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 904         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
 905
 906         if (addr < vma->vm_start || addr >= vma->vm_end)
 907                 return VM_FAULT_SIGBUS;
 908         if (track_pfn_insert(vma, &pgprot, pfn))
 909                 return VM_FAULT_SIGBUS;
 910         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
 911         return VM_FAULT_NOPAGE;
 912 }
 913
 914 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 915                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 916                   struct vm_area_struct *vma)
 917 {
 918         spinlock_t *dst_ptl, *src_ptl;
 919         struct page *src_page;
 920         pmd_t pmd;
 921         pgtable_t pgtable;
 922         int ret;
 923
 924         ret = -ENOMEM;
 925         pgtable = pte_alloc_one(dst_mm, addr);
 926         if (unlikely(!pgtable))
 927                 goto out;
 928
 929         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 930         src_ptl = pmd_lockptr(src_mm, src_pmd);
 931         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 932
 933         ret = -EAGAIN;
 934         pmd = *src_pmd;
 935         if (unlikely(!pmd_trans_huge(pmd))) {
 936                 pte_free(dst_mm, pgtable);
 937                 goto out_unlock;
 938         }
 939         /*
 940          * When page table lock is held, the huge zero pmd should not be
 941          * under splitting since we don't split the page itself, only pmd to
 942          * a page table.
 943          */
 944         if (is_huge_zero_pmd(pmd)) {
 945                 struct page *zero_page;
 946                 /*
 947                  * get_huge_zero_page() will never allocate a new page here,
 948                  * since we already have a zero page to copy. It just takes a
 949                  * reference.
 950                  */
 951                 zero_page = get_huge_zero_page();
 952                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 953                                 zero_page);
 954                 ret = 0;
 955                 goto out_unlock;
 956         }
 957
 958         if (unlikely(pmd_trans_splitting(pmd))) {
 959                 /* split huge page running from under us */
 960                 spin_unlock(src_ptl);
 961                 spin_unlock(dst_ptl);
 962                 pte_free(dst_mm, pgtable);
 963
 964                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 965                 goto out;
 966         }
 967         src_page = pmd_page(pmd);
 968         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 969         get_page(src_page);
 970         page_dup_rmap(src_page);
 971         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 972
 973         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 974         pmd = pmd_mkold(pmd_wrprotect(pmd));
 975         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 976         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 977         atomic_long_inc(&dst_mm->nr_ptes);
 978
 979         ret = 0;
 980 out_unlock:
 981         spin_unlock(src_ptl);
 982         spin_unlock(dst_ptl);
 983 out:
 984         return ret;
 985 }
 986
 987 void huge_pmd_set_accessed(struct mm_struct *mm,
 988                            struct vm_area_struct *vma,
 989                            unsigned long address,
 990                            pmd_t *pmd, pmd_t orig_pmd,
 991                            int dirty)
 992 {
 993         spinlock_t *ptl;
 994         pmd_t entry;
 995         unsigned long haddr;
 996
 997         ptl = pmd_lock(mm, pmd);
 998         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 999                 goto unlock;
1000
1001         entry = pmd_mkyoung(orig_pmd);
1002         haddr = address & HPAGE_PMD_MASK;
1003         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1004                 update_mmu_cache_pmd(vma, address, pmd);
1005
1006 unlock:
1007         spin_unlock(ptl);
1008 }
1009
1010 /*
1011  * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
1012  * during copy_user_huge_page()'s copy_page_rep(): in the case when
1013  * the source page gets split and a tail freed before copy completes.
1014  * Called under pmd_lock of checked pmd, so safe from splitting itself.
1015  */
1016 static void get_user_huge_page(struct page *page)
1017 {
1018         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
1019                 struct page *endpage = page + HPAGE_PMD_NR;
1020
1021                 atomic_add(HPAGE_PMD_NR, &page->_count);
1022                 while (++page < endpage)
1023                         get_huge_page_tail(page);
1024         } else {
1025                 get_page(page);
1026         }
1027 }
1028
1029 static void put_user_huge_page(struct page *page)
1030 {
1031         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
1032                 struct page *endpage = page + HPAGE_PMD_NR;
1033
1034                 while (page < endpage)
1035                         put_page(page++);
1036         } else {
1037                 put_page(page);
1038         }
1039 }
1040
1041 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1042                                         struct vm_area_struct *vma,
1043                                         unsigned long address,
1044                                         pmd_t *pmd, pmd_t orig_pmd,
1045                                         struct page *page,
1046                                         unsigned long haddr)
1047 {
1048         struct mem_cgroup *memcg;
1049         spinlock_t *ptl;
1050         pgtable_t pgtable;
1051         pmd_t _pmd;
1052         int ret = 0, i;
1053         struct page **pages;
1054         unsigned long mmun_start;       /* For mmu_notifiers */
1055         unsigned long mmun_end;         /* For mmu_notifiers */
1056
1057         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1058                         GFP_KERNEL);
1059         if (unlikely(!pages)) {
1060                 ret |= VM_FAULT_OOM;
1061                 goto out;
1062         }
1063
1064         for (i = 0; i < HPAGE_PMD_NR; i++) {
1065                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1066                                                __GFP_OTHER_NODE,
1067                                                vma, address, page_to_nid(page));
1068                 if (unlikely(!pages[i] ||
1069                              mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1070                                                    &memcg))) {
1071                         if (pages[i])
1072                                 put_page(pages[i]);
1073                         while (--i >= 0) {
1074                                 memcg = (void *)page_private(pages[i]);
1075                                 set_page_private(pages[i], 0);
1076                                 mem_cgroup_cancel_charge(pages[i], memcg);
1077                                 put_page(pages[i]);
1078                         }
1079                         kfree(pages);
1080                         ret |= VM_FAULT_OOM;
1081                         goto out;
1082                 }
1083                 set_page_private(pages[i], (unsigned long)memcg);
1084         }
1085
1086         for (i = 0; i < HPAGE_PMD_NR; i++) {
1087                 copy_user_highpage(pages[i], page + i,
1088                                    haddr + PAGE_SIZE * i, vma);
1089                 __SetPageUptodate(pages[i]);
1090                 cond_resched();
1091         }
1092
1093         mmun_start = haddr;
1094         mmun_end   = haddr + HPAGE_PMD_SIZE;
1095         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1096
1097         ptl = pmd_lock(mm, pmd);
1098         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1099                 goto out_free_pages;
1100         VM_BUG_ON_PAGE(!PageHead(page), page);
1101
1102         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1103         /* leave pmd empty until pte is filled */
1104
1105         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1106         pmd_populate(mm, &_pmd, pgtable);
1107
1108         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1109                 pte_t *pte, entry;
1110                 entry = mk_pte(pages[i], vma->vm_page_prot);
1111                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1112                 memcg = (void *)page_private(pages[i]);
1113                 set_page_private(pages[i], 0);
1114                 page_add_new_anon_rmap(pages[i], vma, haddr);
1115                 mem_cgroup_commit_charge(pages[i], memcg, false);
1116                 lru_cache_add_active_or_unevictable(pages[i], vma);
1117                 pte = pte_offset_map(&_pmd, haddr);
1118                 VM_BUG_ON(!pte_none(*pte));
1119                 set_pte_at(mm, haddr, pte, entry);
1120                 pte_unmap(pte);
1121         }
1122         kfree(pages);
1123
1124         smp_wmb(); /* make pte visible before pmd */
1125         pmd_populate(mm, pmd, pgtable);
1126         page_remove_rmap(page);
1127         spin_unlock(ptl);
1128
1129         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1130
1131         ret |= VM_FAULT_WRITE;
1132         put_page(page);
1133
1134 out:
1135         return ret;
1136
1137 out_free_pages:
1138         spin_unlock(ptl);
1139         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1140         for (i = 0; i < HPAGE_PMD_NR; i++) {
1141                 memcg = (void *)page_private(pages[i]);
1142                 set_page_private(pages[i], 0);
1143                 mem_cgroup_cancel_charge(pages[i], memcg);
1144                 put_page(pages[i]);
1145         }
1146         kfree(pages);
1147         goto out;
1148 }
1149
1150 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1151                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1152 {
1153         spinlock_t *ptl;
1154         int ret = 0;
1155         struct page *page = NULL, *new_page;
1156         struct mem_cgroup *memcg;
1157         unsigned long haddr;
1158         unsigned long mmun_start;       /* For mmu_notifiers */
1159         unsigned long mmun_end;         /* For mmu_notifiers */
1160         gfp_t huge_gfp;                 /* for allocation and charge */
1161
1162         ptl = pmd_lockptr(mm, pmd);
1163         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1164         haddr = address & HPAGE_PMD_MASK;
1165         if (is_huge_zero_pmd(orig_pmd))
1166                 goto alloc;
1167         spin_lock(ptl);
1168         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1169                 goto out_unlock;
1170
1171         page = pmd_page(orig_pmd);
1172         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1173         if (page_mapcount(page) == 1) {
1174                 pmd_t entry;
1175                 entry = pmd_mkyoung(orig_pmd);
1176                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1177                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1178                         update_mmu_cache_pmd(vma, address, pmd);
1179                 ret |= VM_FAULT_WRITE;
1180                 goto out_unlock;
1181         }
1182         get_user_huge_page(page);
1183         spin_unlock(ptl);
1184 alloc:
1185         if (transparent_hugepage_enabled(vma) &&
1186             !transparent_hugepage_debug_cow()) {
1187                 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1188                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1189         } else
1190                 new_page = NULL;
1191
1192         if (unlikely(!new_page)) {
1193                 if (!page) {
1194                         split_huge_page_pmd(vma, address, pmd);
1195                         ret |= VM_FAULT_FALLBACK;
1196                 } else {
1197                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1198                                         pmd, orig_pmd, page, haddr);
1199                         if (ret & VM_FAULT_OOM) {
1200                                 split_huge_page(page);
1201                                 ret |= VM_FAULT_FALLBACK;
1202                         }
1203                         put_user_huge_page(page);
1204                 }
1205                 count_vm_event(THP_FAULT_FALLBACK);
1206                 goto out;
1207         }
1208
1209         if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) {
1210                 put_page(new_page);
1211                 if (page) {
1212                         split_huge_page(page);
1213                         put_user_huge_page(page);
1214                 } else
1215                         split_huge_page_pmd(vma, address, pmd);
1216                 ret |= VM_FAULT_FALLBACK;
1217                 count_vm_event(THP_FAULT_FALLBACK);
1218                 goto out;
1219         }
1220
1221         count_vm_event(THP_FAULT_ALLOC);
1222
1223         if (!page)
1224                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1225         else
1226                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1227         __SetPageUptodate(new_page);
1228
1229         mmun_start = haddr;
1230         mmun_end   = haddr + HPAGE_PMD_SIZE;
1231         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1232
1233         spin_lock(ptl);
1234         if (page)
1235                 put_user_huge_page(page);
1236         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1237                 spin_unlock(ptl);
1238                 mem_cgroup_cancel_charge(new_page, memcg);
1239                 put_page(new_page);
1240                 goto out_mn;
1241         } else {
1242                 pmd_t entry;
1243                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1244                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1245                 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1246                 page_add_new_anon_rmap(new_page, vma, haddr);
1247                 mem_cgroup_commit_charge(new_page, memcg, false);
1248                 lru_cache_add_active_or_unevictable(new_page, vma);
1249                 set_pmd_at(mm, haddr, pmd, entry);
1250                 update_mmu_cache_pmd(vma, address, pmd);
1251                 if (!page) {
1252                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1253                         put_huge_zero_page();
1254                 } else {
1255                         VM_BUG_ON_PAGE(!PageHead(page), page);
1256                         page_remove_rmap(page);
1257                         put_page(page);
1258                 }
1259                 ret |= VM_FAULT_WRITE;
1260         }
1261         spin_unlock(ptl);
1262 out_mn:
1263         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1264 out:
1265         return ret;
1266 out_unlock:
1267         spin_unlock(ptl);
1268         return ret;
1269 }
1270
1271 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1272                                    unsigned long addr,
1273                                    pmd_t *pmd,
1274                                    unsigned int flags)
1275 {
1276         struct mm_struct *mm = vma->vm_mm;
1277         struct page *page = NULL;
1278
1279         assert_spin_locked(pmd_lockptr(mm, pmd));
1280
1281         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1282                 goto out;
1283
1284         /* Avoid dumping huge zero page */
1285         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1286                 return ERR_PTR(-EFAULT);
1287
1288         /* Full NUMA hinting faults to serialise migration in fault paths */
1289         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1290                 goto out;
1291
1292         page = pmd_page(*pmd);
1293         VM_BUG_ON_PAGE(!PageHead(page), page);
1294         if (flags & FOLL_TOUCH) {
1295                 pmd_t _pmd;
1296                 /*
1297                  * We should set the dirty bit only for FOLL_WRITE but
1298                  * for now the dirty bit in the pmd is meaningless.
1299                  * And if the dirty bit will become meaningful and
1300                  * we'll only set it with FOLL_WRITE, an atomic
1301                  * set_bit will be required on the pmd to set the
1302                  * young bit, instead of the current set_pmd_at.
1303                  */
1304                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1305                 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1306                                           pmd, _pmd,  1))
1307                         update_mmu_cache_pmd(vma, addr, pmd);
1308         }
1309         if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
1310                 if (page->mapping && trylock_page(page)) {
1311                         lru_add_drain();
1312                         if (page->mapping)
1313                                 mlock_vma_page(page);
1314                         unlock_page(page);
1315                 }
1316         }
1317         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1318         VM_BUG_ON_PAGE(!PageCompound(page), page);
1319         if (flags & FOLL_GET)
1320                 get_page_foll(page);
1321
1322 out:
1323         return page;
1324 }
1325
1326 /* NUMA hinting page fault entry point for trans huge pmds */
1327 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1328                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1329 {
1330         spinlock_t *ptl;
1331         struct anon_vma *anon_vma = NULL;
1332         struct page *page;
1333         unsigned long haddr = addr & HPAGE_PMD_MASK;
1334         int page_nid = -1, this_nid = numa_node_id();
1335         int target_nid, last_cpupid = -1;
1336         bool page_locked;
1337         bool migrated = false;
1338         bool was_writable;
1339         int flags = 0;
1340
1341         /* A PROT_NONE fault should not end up here */
1342         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1343
1344         ptl = pmd_lock(mm, pmdp);
1345         if (unlikely(!pmd_same(pmd, *pmdp)))
1346                 goto out_unlock;
1347
1348         /*
1349          * If there are potential migrations, wait for completion and retry
1350          * without disrupting NUMA hinting information. Do not relock and
1351          * check_same as the page may no longer be mapped.
1352          */
1353         if (unlikely(pmd_trans_migrating(*pmdp))) {
1354                 page = pmd_page(*pmdp);
1355                 spin_unlock(ptl);
1356                 wait_on_page_locked(page);
1357                 goto out;
1358         }
1359
1360         page = pmd_page(pmd);
1361         BUG_ON(is_huge_zero_page(page));
1362         page_nid = page_to_nid(page);
1363         last_cpupid = page_cpupid_last(page);
1364         count_vm_numa_event(NUMA_HINT_FAULTS);
1365         if (page_nid == this_nid) {
1366                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1367                 flags |= TNF_FAULT_LOCAL;
1368         }
1369
1370         /* See similar comment in do_numa_page for explanation */
1371         if (!(vma->vm_flags & VM_WRITE))
1372                 flags |= TNF_NO_GROUP;
1373
1374         /*
1375          * Acquire the page lock to serialise THP migrations but avoid dropping
1376          * page_table_lock if at all possible
1377          */
1378         page_locked = trylock_page(page);
1379         target_nid = mpol_misplaced(page, vma, haddr);
1380         if (target_nid == -1) {
1381                 /* If the page was locked, there are no parallel migrations */
1382                 if (page_locked)
1383                         goto clear_pmdnuma;
1384         }
1385
1386         /* Migration could have started since the pmd_trans_migrating check */
1387         if (!page_locked) {
1388                 spin_unlock(ptl);
1389                 wait_on_page_locked(page);
1390                 page_nid = -1;
1391                 goto out;
1392         }
1393
1394         /*
1395          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1396          * to serialises splits
1397          */
1398         get_page(page);
1399         spin_unlock(ptl);
1400         anon_vma = page_lock_anon_vma_read(page);
1401
1402         /* Confirm the PMD did not change while page_table_lock was released */
1403         spin_lock(ptl);
1404         if (unlikely(!pmd_same(pmd, *pmdp))) {
1405                 unlock_page(page);
1406                 put_page(page);
1407                 page_nid = -1;
1408                 goto out_unlock;
1409         }
1410
1411         /* Bail if we fail to protect against THP splits for any reason */
1412         if (unlikely(!anon_vma)) {
1413                 put_page(page);
1414                 page_nid = -1;
1415                 goto clear_pmdnuma;
1416         }
1417
1418         /*
1419          * Migrate the THP to the requested node, returns with page unlocked
1420          * and access rights restored.
1421          */
1422         spin_unlock(ptl);
1423         migrated = migrate_misplaced_transhuge_page(mm, vma,
1424                                 pmdp, pmd, addr, page, target_nid);
1425         if (migrated) {
1426                 flags |= TNF_MIGRATED;
1427                 page_nid = target_nid;
1428         } else
1429                 flags |= TNF_MIGRATE_FAIL;
1430
1431         goto out;
1432 clear_pmdnuma:
1433         BUG_ON(!PageLocked(page));
1434         was_writable = pmd_write(pmd);
1435         pmd = pmd_modify(pmd, vma->vm_page_prot);
1436         pmd = pmd_mkyoung(pmd);
1437         if (was_writable)
1438                 pmd = pmd_mkwrite(pmd);
1439         set_pmd_at(mm, haddr, pmdp, pmd);
1440         update_mmu_cache_pmd(vma, addr, pmdp);
1441         unlock_page(page);
1442 out_unlock:
1443         spin_unlock(ptl);
1444
1445 out:
1446         if (anon_vma)
1447                 page_unlock_anon_vma_read(anon_vma);
1448
1449         if (page_nid != -1)
1450                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1451
1452         return 0;
1453 }
1454
1455 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1456                  pmd_t *pmd, unsigned long addr)
1457 {
1458         pmd_t orig_pmd;
1459         spinlock_t *ptl;
1460
1461         if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
1462                 return 0;
1463         /*
1464          * For architectures like ppc64 we look at deposited pgtable
1465          * when calling pmdp_huge_get_and_clear. So do the
1466          * pgtable_trans_huge_withdraw after finishing pmdp related
1467          * operations.
1468          */
1469         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1470                         tlb->fullmm);
1471         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1472         if (vma_is_dax(vma)) {
1473                 spin_unlock(ptl);
1474                 if (is_huge_zero_pmd(orig_pmd))
1475                         put_huge_zero_page();
1476         } else if (is_huge_zero_pmd(orig_pmd)) {
1477                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1478                 atomic_long_dec(&tlb->mm->nr_ptes);
1479                 spin_unlock(ptl);
1480                 put_huge_zero_page();
1481         } else {
1482                 struct page *page = pmd_page(orig_pmd);
1483                 page_remove_rmap(page);
1484                 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1485                 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1486                 VM_BUG_ON_PAGE(!PageHead(page), page);
1487                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1488                 atomic_long_dec(&tlb->mm->nr_ptes);
1489                 spin_unlock(ptl);
1490                 tlb_remove_page(tlb, page);
1491         }
1492         return 1;
1493 }
1494
1495 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1496                   unsigned long old_addr,
1497                   unsigned long new_addr, unsigned long old_end,
1498                   pmd_t *old_pmd, pmd_t *new_pmd)
1499 {
1500         spinlock_t *old_ptl, *new_ptl;
1501         int ret = 0;
1502         pmd_t pmd;
1503
1504         struct mm_struct *mm = vma->vm_mm;
1505
1506         if ((old_addr & ~HPAGE_PMD_MASK) ||
1507             (new_addr & ~HPAGE_PMD_MASK) ||
1508             old_end - old_addr < HPAGE_PMD_SIZE ||
1509             (new_vma->vm_flags & VM_NOHUGEPAGE))
1510                 goto out;
1511
1512         /*
1513          * The destination pmd shouldn't be established, free_pgtables()
1514          * should have release it.
1515          */
1516         if (WARN_ON(!pmd_none(*new_pmd))) {
1517                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1518                 goto out;
1519         }
1520
1521         /*
1522          * We don't have to worry about the ordering of src and dst
1523          * ptlocks because exclusive mmap_sem prevents deadlock.
1524          */
1525         ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1526         if (ret == 1) {
1527                 new_ptl = pmd_lockptr(mm, new_pmd);
1528                 if (new_ptl != old_ptl)
1529                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1530                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1531                 VM_BUG_ON(!pmd_none(*new_pmd));
1532
1533                 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1534                         pgtable_t pgtable;
1535                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1536                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1537                 }
1538                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1539                 if (new_ptl != old_ptl)
1540                         spin_unlock(new_ptl);
1541                 spin_unlock(old_ptl);
1542         }
1543 out:
1544         return ret;
1545 }
1546
1547 /*
1548  * Returns
1549  *  - 0 if PMD could not be locked
1550  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1551  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1552  */
1553 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1554                 unsigned long addr, pgprot_t newprot, int prot_numa)
1555 {
1556         struct mm_struct *mm = vma->vm_mm;
1557         spinlock_t *ptl;
1558         int ret = 0;
1559
1560         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1561                 pmd_t entry;
1562                 bool preserve_write = prot_numa && pmd_write(*pmd);
1563                 ret = 1;
1564
1565                 /*
1566                  * Avoid trapping faults against the zero page. The read-only
1567                  * data is likely to be read-cached on the local CPU and
1568                  * local/remote hits to the zero page are not interesting.
1569                  */
1570                 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1571                         spin_unlock(ptl);
1572                         return ret;
1573                 }
1574
1575                 if (!prot_numa || !pmd_protnone(*pmd)) {
1576                         entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1577                         entry = pmd_modify(entry, newprot);
1578                         if (preserve_write)
1579                                 entry = pmd_mkwrite(entry);
1580                         ret = HPAGE_PMD_NR;
1581                         set_pmd_at(mm, addr, pmd, entry);
1582                         BUG_ON(!preserve_write && pmd_write(entry));
1583                 }
1584                 spin_unlock(ptl);
1585         }
1586
1587         return ret;
1588 }
1589
1590 /*
1591  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1592  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1593  *
1594  * Note that if it returns 1, this routine returns without unlocking page
1595  * table locks. So callers must unlock them.
1596  */
1597 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1598                 spinlock_t **ptl)
1599 {
1600         *ptl = pmd_lock(vma->vm_mm, pmd);
1601         if (likely(pmd_trans_huge(*pmd))) {
1602                 if (unlikely(pmd_trans_splitting(*pmd))) {
1603                         spin_unlock(*ptl);
1604                         wait_split_huge_page(vma->anon_vma, pmd);
1605                         return -1;
1606                 } else {
1607                         /* Thp mapped by 'pmd' is stable, so we can
1608                          * handle it as it is. */
1609                         return 1;
1610                 }
1611         }
1612         spin_unlock(*ptl);
1613         return 0;
1614 }
1615
1616 /*
1617  * This function returns whether a given @page is mapped onto the @address
1618  * in the virtual space of @mm.
1619  *
1620  * When it's true, this function returns *pmd with holding the page table lock
1621  * and passing it back to the caller via @ptl.
1622  * If it's false, returns NULL without holding the page table lock.
1623  */
1624 pmd_t *page_check_address_pmd(struct page *page,
1625                               struct mm_struct *mm,
1626                               unsigned long address,
1627                               enum page_check_address_pmd_flag flag,
1628                               spinlock_t **ptl)
1629 {
1630         pgd_t *pgd;
1631         pud_t *pud;
1632         pmd_t *pmd;
1633
1634         if (address & ~HPAGE_PMD_MASK)
1635                 return NULL;
1636
1637         pgd = pgd_offset(mm, address);
1638         if (!pgd_present(*pgd))
1639                 return NULL;
1640         pud = pud_offset(pgd, address);
1641         if (!pud_present(*pud))
1642                 return NULL;
1643         pmd = pmd_offset(pud, address);
1644
1645         *ptl = pmd_lock(mm, pmd);
1646         if (!pmd_present(*pmd))
1647                 goto unlock;
1648         if (pmd_page(*pmd) != page)
1649                 goto unlock;
1650         /*
1651          * split_vma() may create temporary aliased mappings. There is
1652          * no risk as long as all huge pmd are found and have their
1653          * splitting bit set before __split_huge_page_refcount
1654          * runs. Finding the same huge pmd more than once during the
1655          * same rmap walk is not a problem.
1656          */
1657         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1658             pmd_trans_splitting(*pmd))
1659                 goto unlock;
1660         if (pmd_trans_huge(*pmd)) {
1661                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1662                           !pmd_trans_splitting(*pmd));
1663                 return pmd;
1664         }
1665 unlock:
1666         spin_unlock(*ptl);
1667         return NULL;
1668 }
1669
1670 static int __split_huge_page_splitting(struct page *page,
1671                                        struct vm_area_struct *vma,
1672                                        unsigned long address)
1673 {
1674         struct mm_struct *mm = vma->vm_mm;
1675         spinlock_t *ptl;
1676         pmd_t *pmd;
1677         int ret = 0;
1678         /* For mmu_notifiers */
1679         const unsigned long mmun_start = address;
1680         const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1681
1682         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1683         pmd = page_check_address_pmd(page, mm, address,
1684                         PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1685         if (pmd) {
1686                 /*
1687                  * We can't temporarily set the pmd to null in order
1688                  * to split it, the pmd must remain marked huge at all
1689                  * times or the VM won't take the pmd_trans_huge paths
1690                  * and it won't wait on the anon_vma->root->rwsem to
1691                  * serialize against split_huge_page*.
1692                  */
1693                 pmdp_splitting_flush(vma, address, pmd);
1694
1695                 ret = 1;
1696                 spin_unlock(ptl);
1697         }
1698         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1699
1700         return ret;
1701 }
1702
1703 static void __split_huge_page_refcount(struct page *page,
1704                                        struct list_head *list)
1705 {
1706         int i;
1707         struct zone *zone = page_zone(page);
1708         struct lruvec *lruvec;
1709         int tail_count = 0;
1710
1711         /* prevent PageLRU to go away from under us, and freeze lru stats */
1712         spin_lock_irq(&zone->lru_lock);
1713         lruvec = mem_cgroup_page_lruvec(page, zone);
1714
1715         compound_lock(page);
1716         /* complete memcg works before add pages to LRU */
1717         mem_cgroup_split_huge_fixup(page);
1718
1719         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1720                 struct page *page_tail = page + i;
1721
1722                 /* tail_page->_mapcount cannot change */
1723                 BUG_ON(page_mapcount(page_tail) < 0);
1724                 tail_count += page_mapcount(page_tail);
1725                 /* check for overflow */
1726                 BUG_ON(tail_count < 0);
1727                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1728                 /*
1729                  * tail_page->_count is zero and not changing from
1730                  * under us. But get_page_unless_zero() may be running
1731                  * from under us on the tail_page. If we used
1732                  * atomic_set() below instead of atomic_add(), we
1733                  * would then run atomic_set() concurrently with
1734                  * get_page_unless_zero(), and atomic_set() is
1735                  * implemented in C not using locked ops. spin_unlock
1736                  * on x86 sometime uses locked ops because of PPro
1737                  * errata 66, 92, so unless somebody can guarantee
1738                  * atomic_set() here would be safe on all archs (and
1739                  * not only on x86), it's safer to use atomic_add().
1740                  */
1741                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1742                            &page_tail->_count);
1743
1744                 /* after clearing PageTail the gup refcount can be released */
1745                 smp_mb__after_atomic();
1746
1747                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1748                 page_tail->flags |= (page->flags &
1749                                      ((1L << PG_referenced) |
1750                                       (1L << PG_swapbacked) |
1751                                       (1L << PG_mlocked) |
1752                                       (1L << PG_uptodate) |
1753                                       (1L << PG_active) |
1754                                       (1L << PG_unevictable)));
1755                 page_tail->flags |= (1L << PG_dirty);
1756
1757                 /* clear PageTail before overwriting first_page */
1758                 smp_wmb();
1759
1760                 /*
1761                  * __split_huge_page_splitting() already set the
1762                  * splitting bit in all pmd that could map this
1763                  * hugepage, that will ensure no CPU can alter the
1764                  * mapcount on the head page. The mapcount is only
1765                  * accounted in the head page and it has to be
1766                  * transferred to all tail pages in the below code. So
1767                  * for this code to be safe, the split the mapcount
1768                  * can't change. But that doesn't mean userland can't
1769                  * keep changing and reading the page contents while
1770                  * we transfer the mapcount, so the pmd splitting
1771                  * status is achieved setting a reserved bit in the
1772                  * pmd, not by clearing the present bit.
1773                 */
1774                 page_tail->_mapcount = page->_mapcount;
1775
1776                 BUG_ON(page_tail->mapping);
1777                 page_tail->mapping = page->mapping;
1778
1779                 page_tail->index = page->index + i;
1780                 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1781
1782                 BUG_ON(!PageAnon(page_tail));
1783                 BUG_ON(!PageUptodate(page_tail));
1784                 BUG_ON(!PageDirty(page_tail));
1785                 BUG_ON(!PageSwapBacked(page_tail));
1786
1787                 lru_add_page_tail(page, page_tail, lruvec, list);
1788         }
1789         atomic_sub(tail_count, &page->_count);
1790         BUG_ON(atomic_read(&page->_count) <= 0);
1791
1792         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1793
1794         ClearPageCompound(page);
1795         compound_unlock(page);
1796         spin_unlock_irq(&zone->lru_lock);
1797
1798         for (i = 1; i < HPAGE_PMD_NR; i++) {
1799                 struct page *page_tail = page + i;
1800                 BUG_ON(page_count(page_tail) <= 0);
1801                 /*
1802                  * Tail pages may be freed if there wasn't any mapping
1803                  * like if add_to_swap() is running on a lru page that
1804                  * had its mapping zapped. And freeing these pages
1805                  * requires taking the lru_lock so we do the put_page
1806                  * of the tail pages after the split is complete.
1807                  */
1808                 put_page(page_tail);
1809         }
1810
1811         /*
1812          * Only the head page (now become a regular page) is required
1813          * to be pinned by the caller.
1814          */
1815         BUG_ON(page_count(page) <= 0);
1816 }
1817
1818 static int __split_huge_page_map(struct page *page,
1819                                  struct vm_area_struct *vma,
1820                                  unsigned long address)
1821 {
1822         struct mm_struct *mm = vma->vm_mm;
1823         spinlock_t *ptl;
1824         pmd_t *pmd, _pmd;
1825         int ret = 0, i;
1826         pgtable_t pgtable;
1827         unsigned long haddr;
1828
1829         pmd = page_check_address_pmd(page, mm, address,
1830                         PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1831         if (pmd) {
1832                 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1833                 pmd_populate(mm, &_pmd, pgtable);
1834                 if (pmd_write(*pmd))
1835                         BUG_ON(page_mapcount(page) != 1);
1836
1837                 haddr = address;
1838                 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1839                         pte_t *pte, entry;
1840                         BUG_ON(PageCompound(page+i));
1841                         /*
1842                          * Note that NUMA hinting access restrictions are not
1843                          * transferred to avoid any possibility of altering
1844                          * permissions across VMAs.
1845                          */
1846                         entry = mk_pte(page + i, vma->vm_page_prot);
1847                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1848                         if (!pmd_write(*pmd))
1849                                 entry = pte_wrprotect(entry);
1850                         if (!pmd_young(*pmd))
1851                                 entry = pte_mkold(entry);
1852                         pte = pte_offset_map(&_pmd, haddr);
1853                         BUG_ON(!pte_none(*pte));
1854                         set_pte_at(mm, haddr, pte, entry);
1855                         pte_unmap(pte);
1856                 }
1857
1858                 smp_wmb(); /* make pte visible before pmd */
1859                 /*
1860                  * Up to this point the pmd is present and huge and
1861                  * userland has the whole access to the hugepage
1862                  * during the split (which happens in place). If we
1863                  * overwrite the pmd with the not-huge version
1864                  * pointing to the pte here (which of course we could
1865                  * if all CPUs were bug free), userland could trigger
1866                  * a small page size TLB miss on the small sized TLB
1867                  * while the hugepage TLB entry is still established
1868                  * in the huge TLB. Some CPU doesn't like that. See
1869                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1870                  * Erratum 383 on page 93. Intel should be safe but is
1871                  * also warns that it's only safe if the permission
1872                  * and cache attributes of the two entries loaded in
1873                  * the two TLB is identical (which should be the case
1874                  * here). But it is generally safer to never allow
1875                  * small and huge TLB entries for the same virtual
1876                  * address to be loaded simultaneously. So instead of
1877                  * doing "pmd_populate(); flush_tlb_range();" we first
1878                  * mark the current pmd notpresent (atomically because
1879                  * here the pmd_trans_huge and pmd_trans_splitting
1880                  * must remain set at all times on the pmd until the
1881                  * split is complete for this pmd), then we flush the
1882                  * SMP TLB and finally we write the non-huge version
1883                  * of the pmd entry with pmd_populate.
1884                  */
1885                 pmdp_invalidate(vma, address, pmd);
1886                 pmd_populate(mm, pmd, pgtable);
1887                 ret = 1;
1888                 spin_unlock(ptl);
1889         }
1890
1891         return ret;
1892 }
1893
1894 /* must be called with anon_vma->root->rwsem held */
1895 static void __split_huge_page(struct page *page,
1896                               struct anon_vma *anon_vma,
1897                               struct list_head *list)
1898 {
1899         int mapcount, mapcount2;
1900         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1901         struct anon_vma_chain *avc;
1902
1903         BUG_ON(!PageHead(page));
1904         BUG_ON(PageTail(page));
1905
1906         mapcount = 0;
1907         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1908                 struct vm_area_struct *vma = avc->vma;
1909                 unsigned long addr = vma_address(page, vma);
1910                 BUG_ON(is_vma_temporary_stack(vma));
1911                 mapcount += __split_huge_page_splitting(page, vma, addr);
1912         }
1913         /*
1914          * It is critical that new vmas are added to the tail of the
1915          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1916          * and establishes a child pmd before
1917          * __split_huge_page_splitting() freezes the parent pmd (so if
1918          * we fail to prevent copy_huge_pmd() from running until the
1919          * whole __split_huge_page() is complete), we will still see
1920          * the newly established pmd of the child later during the
1921          * walk, to be able to set it as pmd_trans_splitting too.
1922          */
1923         if (mapcount != page_mapcount(page)) {
1924                 pr_err("mapcount %d page_mapcount %d\n",
1925                         mapcount, page_mapcount(page));
1926                 BUG();
1927         }
1928
1929         __split_huge_page_refcount(page, list);
1930
1931         mapcount2 = 0;
1932         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1933                 struct vm_area_struct *vma = avc->vma;
1934                 unsigned long addr = vma_address(page, vma);
1935                 BUG_ON(is_vma_temporary_stack(vma));
1936                 mapcount2 += __split_huge_page_map(page, vma, addr);
1937         }
1938         if (mapcount != mapcount2) {
1939                 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
1940                         mapcount, mapcount2, page_mapcount(page));
1941                 BUG();
1942         }
1943 }
1944
1945 /*
1946  * Split a hugepage into normal pages. This doesn't change the position of head
1947  * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1948  * @list. Both head page and tail pages will inherit mapping, flags, and so on
1949  * from the hugepage.
1950  * Return 0 if the hugepage is split successfully otherwise return 1.
1951  */
1952 int split_huge_page_to_list(struct page *page, struct list_head *list)
1953 {
1954         struct anon_vma *anon_vma;
1955         int ret = 1;
1956
1957         BUG_ON(is_huge_zero_page(page));
1958         BUG_ON(!PageAnon(page));
1959
1960         /*
1961          * The caller does not necessarily hold an mmap_sem that would prevent
1962          * the anon_vma disappearing so we first we take a reference to it
1963          * and then lock the anon_vma for write. This is similar to
1964          * page_lock_anon_vma_read except the write lock is taken to serialise
1965          * against parallel split or collapse operations.
1966          */
1967         anon_vma = page_get_anon_vma(page);
1968         if (!anon_vma)
1969                 goto out;
1970         anon_vma_lock_write(anon_vma);
1971
1972         ret = 0;
1973         if (!PageCompound(page))
1974                 goto out_unlock;
1975
1976         BUG_ON(!PageSwapBacked(page));
1977         __split_huge_page(page, anon_vma, list);
1978         count_vm_event(THP_SPLIT);
1979
1980         BUG_ON(PageCompound(page));
1981 out_unlock:
1982         anon_vma_unlock_write(anon_vma);
1983         put_anon_vma(anon_vma);
1984 out:
1985         return ret;
1986 }
1987
1988 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1989
1990 int hugepage_madvise(struct vm_area_struct *vma,
1991                      unsigned long *vm_flags, int advice)
1992 {
1993         switch (advice) {
1994         case MADV_HUGEPAGE:
1995 #ifdef CONFIG_S390
1996                 /*
1997                  * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1998                  * can't handle this properly after s390_enable_sie, so we simply
1999                  * ignore the madvise to prevent qemu from causing a SIGSEGV.
2000                  */
2001                 if (mm_has_pgste(vma->vm_mm))
2002                         return 0;
2003 #endif
2004                 /*
2005                  * Be somewhat over-protective like KSM for now!
2006                  */
2007                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
2008                         return -EINVAL;
2009                 *vm_flags &= ~VM_NOHUGEPAGE;
2010                 *vm_flags |= VM_HUGEPAGE;
2011                 /*
2012                  * If the vma become good for khugepaged to scan,
2013                  * register it here without waiting a page fault that
2014                  * may not happen any time soon.
2015                  */
2016                 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
2017                         return -ENOMEM;
2018                 break;
2019         case MADV_NOHUGEPAGE:
2020                 /*
2021                  * Be somewhat over-protective like KSM for now!
2022                  */
2023                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
2024                         return -EINVAL;
2025                 *vm_flags &= ~VM_HUGEPAGE;
2026                 *vm_flags |= VM_NOHUGEPAGE;
2027                 /*
2028                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
2029                  * this vma even if we leave the mm registered in khugepaged if
2030                  * it got registered before VM_NOHUGEPAGE was set.
2031                  */
2032                 break;
2033         }
2034
2035         return 0;
2036 }
2037
2038 static int __init khugepaged_slab_init(void)
2039 {
2040         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
2041                                           sizeof(struct mm_slot),
2042                                           __alignof__(struct mm_slot), 0, NULL);
2043         if (!mm_slot_cache)
2044                 return -ENOMEM;
2045
2046         return 0;
2047 }
2048
2049 static void __init khugepaged_slab_exit(void)
2050 {
2051         kmem_cache_destroy(mm_slot_cache);
2052 }
2053
2054 static inline struct mm_slot *alloc_mm_slot(void)
2055 {
2056         if (!mm_slot_cache)     /* initialization failed */
2057                 return NULL;
2058         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
2059 }
2060
2061 static inline void free_mm_slot(struct mm_slot *mm_slot)
2062 {
2063         kmem_cache_free(mm_slot_cache, mm_slot);
2064 }
2065
2066 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
2067 {
2068         struct mm_slot *mm_slot;
2069
2070         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
2071                 if (mm == mm_slot->mm)
2072                         return mm_slot;
2073
2074         return NULL;
2075 }
2076
2077 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2078                                     struct mm_slot *mm_slot)
2079 {
2080         mm_slot->mm = mm;
2081         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2082 }
2083
2084 static inline int khugepaged_test_exit(struct mm_struct *mm)
2085 {
2086         return atomic_read(&mm->mm_users) == 0;
2087 }
2088
2089 int __khugepaged_enter(struct mm_struct *mm)
2090 {
2091         struct mm_slot *mm_slot;
2092         int wakeup;
2093
2094         mm_slot = alloc_mm_slot();
2095         if (!mm_slot)
2096                 return -ENOMEM;
2097
2098         /* __khugepaged_exit() must not run from under us */
2099         VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
2100         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2101                 free_mm_slot(mm_slot);
2102                 return 0;
2103         }
2104
2105         spin_lock(&khugepaged_mm_lock);
2106         insert_to_mm_slots_hash(mm, mm_slot);
2107         /*
2108          * Insert just behind the scanning cursor, to let the area settle
2109          * down a little.
2110          */
2111         wakeup = list_empty(&khugepaged_scan.mm_head);
2112         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2113         spin_unlock(&khugepaged_mm_lock);
2114
2115         atomic_inc(&mm->mm_count);
2116         if (wakeup)
2117                 wake_up_interruptible(&khugepaged_wait);
2118
2119         return 0;
2120 }
2121
2122 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2123                                unsigned long vm_flags)
2124 {
2125         unsigned long hstart, hend;
2126         if (!vma->anon_vma)
2127                 /*
2128                  * Not yet faulted in so we will register later in the
2129                  * page fault if needed.
2130                  */
2131                 return 0;
2132         if (vma->vm_ops)
2133                 /* khugepaged not yet working on file or special mappings */
2134                 return 0;
2135         VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
2136         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2137         hend = vma->vm_end & HPAGE_PMD_MASK;
2138         if (hstart < hend)
2139                 return khugepaged_enter(vma, vm_flags);
2140         return 0;
2141 }
2142
2143 void __khugepaged_exit(struct mm_struct *mm)
2144 {
2145         struct mm_slot *mm_slot;
2146         int free = 0;
2147
2148         spin_lock(&khugepaged_mm_lock);
2149         mm_slot = get_mm_slot(mm);
2150         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2151                 hash_del(&mm_slot->hash);
2152                 list_del(&mm_slot->mm_node);
2153                 free = 1;
2154         }
2155         spin_unlock(&khugepaged_mm_lock);
2156
2157         if (free) {
2158                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2159                 free_mm_slot(mm_slot);
2160                 mmdrop(mm);
2161         } else if (mm_slot) {
2162                 /*
2163                  * This is required to serialize against
2164                  * khugepaged_test_exit() (which is guaranteed to run
2165                  * under mmap sem read mode). Stop here (after we
2166                  * return all pagetables will be destroyed) until
2167                  * khugepaged has finished working on the pagetables
2168                  * under the mmap_sem.
2169                  */
2170                 down_write(&mm->mmap_sem);
2171                 up_write(&mm->mmap_sem);
2172         }
2173 }
2174
2175 static void release_pte_page(struct page *page)
2176 {
2177         /* 0 stands for page_is_file_cache(page) == false */
2178         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2179         unlock_page(page);
2180         putback_lru_page(page);
2181 }
2182
2183 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2184 {
2185         while (--_pte >= pte) {
2186                 pte_t pteval = *_pte;
2187                 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2188                         release_pte_page(pte_page(pteval));
2189         }
2190 }
2191
2192 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2193                                         unsigned long address,
2194                                         pte_t *pte)
2195 {
2196         struct page *page;
2197         pte_t *_pte;
2198         int none_or_zero = 0;
2199         bool referenced = false, writable = false;
2200         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2201              _pte++, address += PAGE_SIZE) {
2202                 pte_t pteval = *_pte;
2203                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2204                         if (!userfaultfd_armed(vma) &&
2205                             ++none_or_zero <= khugepaged_max_ptes_none)
2206                                 continue;
2207                         else
2208                                 goto out;
2209                 }
2210                 if (!pte_present(pteval))
2211                         goto out;
2212                 page = vm_normal_page(vma, address, pteval);
2213                 if (unlikely(!page))
2214                         goto out;
2215
2216                 VM_BUG_ON_PAGE(PageCompound(page), page);
2217                 VM_BUG_ON_PAGE(!PageAnon(page), page);
2218                 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2219
2220                 /*
2221                  * We can do it before isolate_lru_page because the
2222                  * page can't be freed from under us. NOTE: PG_lock
2223                  * is needed to serialize against split_huge_page
2224                  * when invoked from the VM.
2225                  */
2226                 if (!trylock_page(page))
2227                         goto out;
2228
2229                 /*
2230                  * cannot use mapcount: can't collapse if there's a gup pin.
2231                  * The page must only be referenced by the scanned process
2232                  * and page swap cache.
2233                  */
2234                 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2235                         unlock_page(page);
2236                         goto out;
2237                 }
2238                 if (pte_write(pteval)) {
2239                         writable = true;
2240                 } else {
2241                         if (PageSwapCache(page) && !reuse_swap_page(page)) {
2242                                 unlock_page(page);
2243                                 goto out;
2244                         }
2245                         /*
2246                          * Page is not in the swap cache. It can be collapsed
2247                          * into a THP.
2248                          */
2249                 }
2250
2251                 /*
2252                  * Isolate the page to avoid collapsing an hugepage
2253                  * currently in use by the VM.
2254                  */
2255                 if (isolate_lru_page(page)) {
2256                         unlock_page(page);
2257                         goto out;
2258                 }
2259                 /* 0 stands for page_is_file_cache(page) == false */
2260                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2261                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2262                 VM_BUG_ON_PAGE(PageLRU(page), page);
2263
2264                 /* If there is no mapped pte young don't collapse the page */
2265                 if (pte_young(pteval) || PageReferenced(page) ||
2266                     mmu_notifier_test_young(vma->vm_mm, address))
2267                         referenced = true;
2268         }
2269         if (likely(referenced && writable))
2270                 return 1;
2271 out:
2272         release_pte_pages(pte, _pte);
2273         return 0;
2274 }
2275
2276 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2277                                       struct vm_area_struct *vma,
2278                                       unsigned long address,
2279                                       spinlock_t *ptl)
2280 {
2281         pte_t *_pte;
2282         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2283                 pte_t pteval = *_pte;
2284                 struct page *src_page;
2285
2286                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2287                         clear_user_highpage(page, address);
2288                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2289                         if (is_zero_pfn(pte_pfn(pteval))) {
2290                                 /*
2291                                  * ptl mostly unnecessary.
2292                                  */
2293                                 spin_lock(ptl);
2294                                 /*
2295                                  * paravirt calls inside pte_clear here are
2296                                  * superfluous.
2297                                  */
2298                                 pte_clear(vma->vm_mm, address, _pte);
2299                                 spin_unlock(ptl);
2300                         }
2301                 } else {
2302                         src_page = pte_page(pteval);
2303                         copy_user_highpage(page, src_page, address, vma);
2304                         VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2305                         release_pte_page(src_page);
2306                         /*
2307                          * ptl mostly unnecessary, but preempt has to
2308                          * be disabled to update the per-cpu stats
2309                          * inside page_remove_rmap().
2310                          */
2311                         spin_lock(ptl);
2312                         /*
2313                          * paravirt calls inside pte_clear here are
2314                          * superfluous.
2315                          */
2316                         pte_clear(vma->vm_mm, address, _pte);
2317                         page_remove_rmap(src_page);
2318                         spin_unlock(ptl);
2319                         free_page_and_swap_cache(src_page);
2320                 }
2321
2322                 address += PAGE_SIZE;
2323                 page++;
2324         }
2325 }
2326
2327 static void khugepaged_alloc_sleep(void)
2328 {
2329         DEFINE_WAIT(wait);
2330
2331         add_wait_queue(&khugepaged_wait, &wait);
2332         freezable_schedule_timeout_interruptible(
2333                 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2334         remove_wait_queue(&khugepaged_wait, &wait);
2335 }
2336
2337 static int khugepaged_node_load[MAX_NUMNODES];
2338
2339 static bool khugepaged_scan_abort(int nid)
2340 {
2341         int i;
2342
2343         /*
2344          * If zone_reclaim_mode is disabled, then no extra effort is made to
2345          * allocate memory locally.
2346          */
2347         if (!zone_reclaim_mode)
2348                 return false;
2349
2350         /* If there is a count for this node already, it must be acceptable */
2351         if (khugepaged_node_load[nid])
2352                 return false;
2353
2354         for (i = 0; i < MAX_NUMNODES; i++) {
2355                 if (!khugepaged_node_load[i])
2356                         continue;
2357                 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2358                         return true;
2359         }
2360         return false;
2361 }
2362
2363 #ifdef CONFIG_NUMA
2364 static int khugepaged_find_target_node(void)
2365 {
2366         static int last_khugepaged_target_node = NUMA_NO_NODE;
2367         int nid, target_node = 0, max_value = 0;
2368
2369         /* find first node with max normal pages hit */
2370         for (nid = 0; nid < MAX_NUMNODES; nid++)
2371                 if (khugepaged_node_load[nid] > max_value) {
2372                         max_value = khugepaged_node_load[nid];
2373                         target_node = nid;
2374                 }
2375
2376         /* do some balance if several nodes have the same hit record */
2377         if (target_node <= last_khugepaged_target_node)
2378                 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2379                                 nid++)
2380                         if (max_value == khugepaged_node_load[nid]) {
2381                                 target_node = nid;
2382                                 break;
2383                         }
2384
2385         last_khugepaged_target_node = target_node;
2386         return target_node;
2387 }
2388
2389 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2390 {
2391         if (IS_ERR(*hpage)) {
2392                 if (!*wait)
2393                         return false;
2394
2395                 *wait = false;
2396                 *hpage = NULL;
2397                 khugepaged_alloc_sleep();
2398         } else if (*hpage) {
2399                 put_page(*hpage);
2400                 *hpage = NULL;
2401         }
2402
2403         return true;
2404 }
2405
2406 static struct page *
2407 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2408                        struct vm_area_struct *vma, unsigned long address,
2409                        int node)
2410 {
2411         VM_BUG_ON_PAGE(*hpage, *hpage);
2412
2413         /*
2414          * Before allocating the hugepage, release the mmap_sem read lock.
2415          * The allocation can take potentially a long time if it involves
2416          * sync compaction, and we do not need to hold the mmap_sem during
2417          * that. We will recheck the vma after taking it again in write mode.
2418          */
2419         up_read(&mm->mmap_sem);
2420
2421         *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2422         if (unlikely(!*hpage)) {
2423                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2424                 *hpage = ERR_PTR(-ENOMEM);
2425                 return NULL;
2426         }
2427
2428         count_vm_event(THP_COLLAPSE_ALLOC);
2429         return *hpage;
2430 }
2431 #else
2432 static int khugepaged_find_target_node(void)
2433 {
2434         return 0;
2435 }
2436
2437 static inline struct page *alloc_hugepage(int defrag)
2438 {
2439         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2440                            HPAGE_PMD_ORDER);
2441 }
2442
2443 static struct page *khugepaged_alloc_hugepage(bool *wait)
2444 {
2445         struct page *hpage;
2446
2447         do {
2448                 hpage = alloc_hugepage(khugepaged_defrag());
2449                 if (!hpage) {
2450                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2451                         if (!*wait)
2452                                 return NULL;
2453
2454                         *wait = false;
2455                         khugepaged_alloc_sleep();
2456                 } else
2457                         count_vm_event(THP_COLLAPSE_ALLOC);
2458         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2459
2460         return hpage;
2461 }
2462
2463 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2464 {
2465         if (!*hpage)
2466                 *hpage = khugepaged_alloc_hugepage(wait);
2467
2468         if (unlikely(!*hpage))
2469                 return false;
2470
2471         return true;
2472 }
2473
2474 static struct page *
2475 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2476                        struct vm_area_struct *vma, unsigned long address,
2477                        int node)
2478 {
2479         up_read(&mm->mmap_sem);
2480         VM_BUG_ON(!*hpage);
2481
2482         return  *hpage;
2483 }
2484 #endif
2485
2486 static bool hugepage_vma_check(struct vm_area_struct *vma)
2487 {
2488         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2489             (vma->vm_flags & VM_NOHUGEPAGE))
2490                 return false;
2491
2492         if (!vma->anon_vma || vma->vm_ops)
2493                 return false;
2494         if (is_vma_temporary_stack(vma))
2495                 return false;
2496         VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2497         return true;
2498 }
2499
2500 static void collapse_huge_page(struct mm_struct *mm,
2501                                    unsigned long address,
2502                                    struct page **hpage,
2503                                    struct vm_area_struct *vma,
2504                                    int node)
2505 {
2506         pmd_t *pmd, _pmd;
2507         pte_t *pte;
2508         pgtable_t pgtable;
2509         struct page *new_page;
2510         spinlock_t *pmd_ptl, *pte_ptl;
2511         int isolated;
2512         unsigned long hstart, hend;
2513         struct mem_cgroup *memcg;
2514         unsigned long mmun_start;       /* For mmu_notifiers */
2515         unsigned long mmun_end;         /* For mmu_notifiers */
2516         gfp_t gfp;
2517
2518         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2519
2520         /* Only allocate from the target node */
2521         gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2522                 __GFP_THISNODE;
2523
2524         /* release the mmap_sem read lock. */
2525         new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node);
2526         if (!new_page)
2527                 return;
2528
2529         if (unlikely(mem_cgroup_try_charge(new_page, mm,
2530                                            gfp, &memcg)))
2531                 return;
2532
2533         /*
2534          * Prevent all access to pagetables with the exception of
2535          * gup_fast later hanlded by the ptep_clear_flush and the VM
2536          * handled by the anon_vma lock + PG_lock.
2537          */
2538         down_write(&mm->mmap_sem);
2539         if (unlikely(khugepaged_test_exit(mm)))
2540                 goto out;
2541
2542         vma = find_vma(mm, address);
2543         if (!vma)
2544                 goto out;
2545         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2546         hend = vma->vm_end & HPAGE_PMD_MASK;
2547         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2548                 goto out;
2549         if (!hugepage_vma_check(vma))
2550                 goto out;
2551         pmd = mm_find_pmd(mm, address);
2552         if (!pmd)
2553                 goto out;
2554
2555         anon_vma_lock_write(vma->anon_vma);
2556
2557         pte = pte_offset_map(pmd, address);
2558         pte_ptl = pte_lockptr(mm, pmd);
2559
2560         mmun_start = address;
2561         mmun_end   = address + HPAGE_PMD_SIZE;
2562         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2563         pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2564         /*
2565          * After this gup_fast can't run anymore. This also removes
2566          * any huge TLB entry from the CPU so we won't allow
2567          * huge and small TLB entries for the same virtual address
2568          * to avoid the risk of CPU bugs in that area.
2569          */
2570         _pmd = pmdp_collapse_flush(vma, address, pmd);
2571         spin_unlock(pmd_ptl);
2572         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2573
2574         spin_lock(pte_ptl);
2575         isolated = __collapse_huge_page_isolate(vma, address, pte);
2576         spin_unlock(pte_ptl);
2577
2578         if (unlikely(!isolated)) {
2579                 pte_unmap(pte);
2580                 spin_lock(pmd_ptl);
2581                 BUG_ON(!pmd_none(*pmd));
2582                 /*
2583                  * We can only use set_pmd_at when establishing
2584                  * hugepmds and never for establishing regular pmds that
2585                  * points to regular pagetables. Use pmd_populate for that
2586                  */
2587                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2588                 spin_unlock(pmd_ptl);
2589                 anon_vma_unlock_write(vma->anon_vma);
2590                 goto out;
2591         }
2592
2593         /*
2594          * All pages are isolated and locked so anon_vma rmap
2595          * can't run anymore.
2596          */
2597         anon_vma_unlock_write(vma->anon_vma);
2598
2599         __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2600         pte_unmap(pte);
2601         __SetPageUptodate(new_page);
2602         pgtable = pmd_pgtable(_pmd);
2603
2604         _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2605         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2606
2607         /*
2608          * spin_lock() below is not the equivalent of smp_wmb(), so
2609          * this is needed to avoid the copy_huge_page writes to become
2610          * visible after the set_pmd_at() write.
2611          */
2612         smp_wmb();
2613
2614         spin_lock(pmd_ptl);
2615         BUG_ON(!pmd_none(*pmd));
2616         page_add_new_anon_rmap(new_page, vma, address);
2617         mem_cgroup_commit_charge(new_page, memcg, false);
2618         lru_cache_add_active_or_unevictable(new_page, vma);
2619         pgtable_trans_huge_deposit(mm, pmd, pgtable);
2620         set_pmd_at(mm, address, pmd, _pmd);
2621         update_mmu_cache_pmd(vma, address, pmd);
2622         spin_unlock(pmd_ptl);
2623
2624         *hpage = NULL;
2625
2626         khugepaged_pages_collapsed++;
2627 out_up_write:
2628         up_write(&mm->mmap_sem);
2629         return;
2630
2631 out:
2632         mem_cgroup_cancel_charge(new_page, memcg);
2633         goto out_up_write;
2634 }
2635
2636 static int khugepaged_scan_pmd(struct mm_struct *mm,
2637                                struct vm_area_struct *vma,
2638                                unsigned long address,
2639                                struct page **hpage)
2640 {
2641         pmd_t *pmd;
2642         pte_t *pte, *_pte;
2643         int ret = 0, none_or_zero = 0;
2644         struct page *page;
2645         unsigned long _address;
2646         spinlock_t *ptl;
2647         int node = NUMA_NO_NODE;
2648         bool writable = false, referenced = false;
2649
2650         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2651
2652         pmd = mm_find_pmd(mm, address);
2653         if (!pmd)
2654                 goto out;
2655
2656         memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2657         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2658         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2659              _pte++, _address += PAGE_SIZE) {
2660                 pte_t pteval = *_pte;
2661                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2662                         if (!userfaultfd_armed(vma) &&
2663                             ++none_or_zero <= khugepaged_max_ptes_none)
2664                                 continue;
2665                         else
2666                                 goto out_unmap;
2667                 }
2668                 if (!pte_present(pteval))
2669                         goto out_unmap;
2670                 if (pte_write(pteval))
2671                         writable = true;
2672
2673                 page = vm_normal_page(vma, _address, pteval);
2674                 if (unlikely(!page))
2675                         goto out_unmap;
2676                 /*
2677                  * Record which node the original page is from and save this
2678                  * information to khugepaged_node_load[].
2679                  * Khupaged will allocate hugepage from the node has the max
2680                  * hit record.
2681                  */
2682                 node = page_to_nid(page);
2683                 if (khugepaged_scan_abort(node))
2684                         goto out_unmap;
2685                 khugepaged_node_load[node]++;
2686                 VM_BUG_ON_PAGE(PageCompound(page), page);
2687                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2688                         goto out_unmap;
2689                 /*
2690                  * cannot use mapcount: can't collapse if there's a gup pin.
2691                  * The page must only be referenced by the scanned process
2692                  * and page swap cache.
2693                  */
2694                 if (page_count(page) != 1 + !!PageSwapCache(page))
2695                         goto out_unmap;
2696                 if (pte_young(pteval) || PageReferenced(page) ||
2697                     mmu_notifier_test_young(vma->vm_mm, address))
2698                         referenced = true;
2699         }
2700         if (referenced && writable)
2701                 ret = 1;
2702 out_unmap:
2703         pte_unmap_unlock(pte, ptl);
2704         if (ret) {
2705                 node = khugepaged_find_target_node();
2706                 /* collapse_huge_page will return with the mmap_sem released */
2707                 collapse_huge_page(mm, address, hpage, vma, node);
2708         }
2709 out:
2710         return ret;
2711 }
2712
2713 static void collect_mm_slot(struct mm_slot *mm_slot)
2714 {
2715         struct mm_struct *mm = mm_slot->mm;
2716
2717         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2718
2719         if (khugepaged_test_exit(mm)) {
2720                 /* free mm_slot */
2721                 hash_del(&mm_slot->hash);
2722                 list_del(&mm_slot->mm_node);
2723
2724                 /*
2725                  * Not strictly needed because the mm exited already.
2726                  *
2727                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2728                  */
2729
2730                 /* khugepaged_mm_lock actually not necessary for the below */
2731                 free_mm_slot(mm_slot);
2732                 mmdrop(mm);
2733         }
2734 }
2735
2736 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2737                                             struct page **hpage)
2738         __releases(&khugepaged_mm_lock)
2739         __acquires(&khugepaged_mm_lock)
2740 {
2741         struct mm_slot *mm_slot;
2742         struct mm_struct *mm;
2743         struct vm_area_struct *vma;
2744         int progress = 0;
2745
2746         VM_BUG_ON(!pages);
2747         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2748
2749         if (khugepaged_scan.mm_slot)
2750                 mm_slot = khugepaged_scan.mm_slot;
2751         else {
2752                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2753                                      struct mm_slot, mm_node);
2754                 khugepaged_scan.address = 0;
2755                 khugepaged_scan.mm_slot = mm_slot;
2756         }
2757         spin_unlock(&khugepaged_mm_lock);
2758
2759         mm = mm_slot->mm;
2760         down_read(&mm->mmap_sem);
2761         if (unlikely(khugepaged_test_exit(mm)))
2762                 vma = NULL;
2763         else
2764                 vma = find_vma(mm, khugepaged_scan.address);
2765
2766         progress++;
2767         for (; vma; vma = vma->vm_next) {
2768                 unsigned long hstart, hend;
2769
2770                 cond_resched();
2771                 if (unlikely(khugepaged_test_exit(mm))) {
2772                         progress++;
2773                         break;
2774                 }
2775                 if (!hugepage_vma_check(vma)) {
2776 skip:
2777                         progress++;
2778                         continue;
2779                 }
2780                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2781                 hend = vma->vm_end & HPAGE_PMD_MASK;
2782                 if (hstart >= hend)
2783                         goto skip;
2784                 if (khugepaged_scan.address > hend)
2785                         goto skip;
2786                 if (khugepaged_scan.address < hstart)
2787                         khugepaged_scan.address = hstart;
2788                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2789
2790                 while (khugepaged_scan.address < hend) {
2791                         int ret;
2792                         cond_resched();
2793                         if (unlikely(khugepaged_test_exit(mm)))
2794                                 goto breakouterloop;
2795
2796                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2797                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2798                                   hend);
2799                         ret = khugepaged_scan_pmd(mm, vma,
2800                                                   khugepaged_scan.address,
2801                                                   hpage);
2802                         /* move to next address */
2803                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2804                         progress += HPAGE_PMD_NR;
2805                         if (ret)
2806                                 /* we released mmap_sem so break loop */
2807                                 goto breakouterloop_mmap_sem;
2808                         if (progress >= pages)
2809                                 goto breakouterloop;
2810                 }
2811         }
2812 breakouterloop:
2813         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2814 breakouterloop_mmap_sem:
2815
2816         spin_lock(&khugepaged_mm_lock);
2817         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2818         /*
2819          * Release the current mm_slot if this mm is about to die, or
2820          * if we scanned all vmas of this mm.
2821          */
2822         if (khugepaged_test_exit(mm) || !vma) {
2823                 /*
2824                  * Make sure that if mm_users is reaching zero while
2825                  * khugepaged runs here, khugepaged_exit will find
2826                  * mm_slot not pointing to the exiting mm.
2827                  */
2828                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2829                         khugepaged_scan.mm_slot = list_entry(
2830                                 mm_slot->mm_node.next,
2831                                 struct mm_slot, mm_node);
2832                         khugepaged_scan.address = 0;
2833                 } else {
2834                         khugepaged_scan.mm_slot = NULL;
2835                         khugepaged_full_scans++;
2836                 }
2837
2838                 collect_mm_slot(mm_slot);
2839         }
2840
2841         return progress;
2842 }
2843
2844 static int khugepaged_has_work(void)
2845 {
2846         return !list_empty(&khugepaged_scan.mm_head) &&
2847                 khugepaged_enabled();
2848 }
2849
2850 static int khugepaged_wait_event(void)
2851 {
2852         return !list_empty(&khugepaged_scan.mm_head) ||
2853                 kthread_should_stop();
2854 }
2855
2856 static void khugepaged_do_scan(void)
2857 {
2858         struct page *hpage = NULL;
2859         unsigned int progress = 0, pass_through_head = 0;
2860         unsigned int pages = khugepaged_pages_to_scan;
2861         bool wait = true;
2862
2863         barrier(); /* write khugepaged_pages_to_scan to local stack */
2864
2865         while (progress < pages) {
2866                 if (!khugepaged_prealloc_page(&hpage, &wait))
2867                         break;
2868
2869                 cond_resched();
2870
2871                 if (unlikely(kthread_should_stop() || try_to_freeze()))
2872                         break;
2873
2874                 spin_lock(&khugepaged_mm_lock);
2875                 if (!khugepaged_scan.mm_slot)
2876                         pass_through_head++;
2877                 if (khugepaged_has_work() &&
2878                     pass_through_head < 2)
2879                         progress += khugepaged_scan_mm_slot(pages - progress,
2880                                                             &hpage);
2881                 else
2882                         progress = pages;
2883                 spin_unlock(&khugepaged_mm_lock);
2884         }
2885
2886         if (!IS_ERR_OR_NULL(hpage))
2887                 put_page(hpage);
2888 }
2889
2890 static void khugepaged_wait_work(void)
2891 {
2892         if (khugepaged_has_work()) {
2893                 if (!khugepaged_scan_sleep_millisecs)
2894                         return;
2895
2896                 wait_event_freezable_timeout(khugepaged_wait,
2897                                              kthread_should_stop(),
2898                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2899                 return;
2900         }
2901
2902         if (khugepaged_enabled())
2903                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2904 }
2905
2906 static int khugepaged(void *none)
2907 {
2908         struct mm_slot *mm_slot;
2909
2910         set_freezable();
2911         set_user_nice(current, MAX_NICE);
2912
2913         while (!kthread_should_stop()) {
2914                 khugepaged_do_scan();
2915                 khugepaged_wait_work();
2916         }
2917
2918         spin_lock(&khugepaged_mm_lock);
2919         mm_slot = khugepaged_scan.mm_slot;
2920         khugepaged_scan.mm_slot = NULL;
2921         if (mm_slot)
2922                 collect_mm_slot(mm_slot);
2923         spin_unlock(&khugepaged_mm_lock);
2924         return 0;
2925 }
2926
2927 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2928                 unsigned long haddr, pmd_t *pmd)
2929 {
2930         struct mm_struct *mm = vma->vm_mm;
2931         pgtable_t pgtable;
2932         pmd_t _pmd;
2933         int i;
2934
2935         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2936         /* leave pmd empty until pte is filled */
2937
2938         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2939         pmd_populate(mm, &_pmd, pgtable);
2940
2941         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2942                 pte_t *pte, entry;
2943                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2944                 entry = pte_mkspecial(entry);
2945                 pte = pte_offset_map(&_pmd, haddr);
2946                 VM_BUG_ON(!pte_none(*pte));
2947                 set_pte_at(mm, haddr, pte, entry);
2948                 pte_unmap(pte);
2949         }
2950         smp_wmb(); /* make pte visible before pmd */
2951         pmd_populate(mm, pmd, pgtable);
2952         put_huge_zero_page();
2953 }
2954
2955 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2956                 pmd_t *pmd)
2957 {
2958         spinlock_t *ptl;
2959         struct page *page = NULL;
2960         struct mm_struct *mm = vma->vm_mm;
2961         unsigned long haddr = address & HPAGE_PMD_MASK;
2962         unsigned long mmun_start;       /* For mmu_notifiers */
2963         unsigned long mmun_end;         /* For mmu_notifiers */
2964
2965         BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2966
2967         mmun_start = haddr;
2968         mmun_end   = haddr + HPAGE_PMD_SIZE;
2969 again:
2970         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2971         ptl = pmd_lock(mm, pmd);
2972         if (unlikely(!pmd_trans_huge(*pmd)))
2973                 goto unlock;
2974         if (vma_is_dax(vma)) {
2975                 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2976                 if (is_huge_zero_pmd(_pmd))
2977                         put_huge_zero_page();
2978         } else if (is_huge_zero_pmd(*pmd)) {
2979                 __split_huge_zero_page_pmd(vma, haddr, pmd);
2980         } else {
2981                 page = pmd_page(*pmd);
2982                 VM_BUG_ON_PAGE(!page_count(page), page);
2983                 get_page(page);
2984         }
2985  unlock:
2986         spin_unlock(ptl);
2987         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2988
2989         if (!page)
2990                 return;
2991
2992         split_huge_page(page);
2993         put_page(page);
2994
2995         /*
2996          * We don't always have down_write of mmap_sem here: a racing
2997          * do_huge_pmd_wp_page() might have copied-on-write to another
2998          * huge page before our split_huge_page() got the anon_vma lock.
2999          */
3000         if (unlikely(pmd_trans_huge(*pmd)))
3001                 goto again;
3002 }
3003
3004 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
3005                 pmd_t *pmd)
3006 {
3007         struct vm_area_struct *vma;
3008
3009         vma = find_vma(mm, address);
3010         BUG_ON(vma == NULL);
3011         split_huge_page_pmd(vma, address, pmd);
3012 }
3013
3014 static void split_huge_page_address(struct mm_struct *mm,
3015                                     unsigned long address)
3016 {
3017         pgd_t *pgd;
3018         pud_t *pud;
3019         pmd_t *pmd;
3020
3021         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
3022
3023         pgd = pgd_offset(mm, address);
3024         if (!pgd_present(*pgd))
3025                 return;
3026
3027         pud = pud_offset(pgd, address);
3028         if (!pud_present(*pud))
3029                 return;
3030
3031         pmd = pmd_offset(pud, address);
3032         if (!pmd_present(*pmd))
3033                 return;
3034         /*
3035          * Caller holds the mmap_sem write mode, so a huge pmd cannot
3036          * materialize from under us.
3037          */
3038         split_huge_page_pmd_mm(mm, address, pmd);
3039 }
3040
3041 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3042                              unsigned long start,
3043                              unsigned long end,
3044                              long adjust_next)
3045 {
3046         /*
3047          * If the new start address isn't hpage aligned and it could
3048          * previously contain an hugepage: check if we need to split
3049          * an huge pmd.
3050          */
3051         if (start & ~HPAGE_PMD_MASK &&
3052             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3053             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3054                 split_huge_page_address(vma->vm_mm, start);
3055
3056         /*
3057          * If the new end address isn't hpage aligned and it could
3058          * previously contain an hugepage: check if we need to split
3059          * an huge pmd.
3060          */
3061         if (end & ~HPAGE_PMD_MASK &&
3062             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3063             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3064                 split_huge_page_address(vma->vm_mm, end);
3065
3066         /*
3067          * If we're also updating the vma->vm_next->vm_start, if the new
3068          * vm_next->vm_start isn't page aligned and it could previously
3069          * contain an hugepage: check if we need to split an huge pmd.
3070          */
3071         if (adjust_next > 0) {
3072                 struct vm_area_struct *next = vma->vm_next;
3073                 unsigned long nstart = next->vm_start;
3074                 nstart += adjust_next << PAGE_SHIFT;
3075                 if (nstart & ~HPAGE_PMD_MASK &&
3076                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3077                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3078                         split_huge_page_address(next->vm_mm, nstart);
3079         }
3080 }